This violates the second law of thermodynamics as well as the theory of the 'arrow of time' which states time can only flow forwards. These experiments have proven that time can work in reverse (atoms being heated up will get hotter instead of getting colder).

I'm wondering how long it'd take for scientists to scale this up. Eg. take an animal or person a few minutes into the past? I had a best friend die abruptly in 2013, would it be possible to go back in time to see him again?

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This violates the second law of thermodynamics as well as the theory of the 'arrow of time' which states time can only flow forwards. These experiments have proven that time can work in reverse (atoms being heated up will get hotter instead of getting colder).

I'm wondering how long it'd take for scientists to scale this up. Eg. take an animal or person a few minutes into the past? I had a best friend die abruptly in 2013, would it be possible to go back in time to see him again?

The effect is NOT a reversal of time, but a short-term apparent violation of the 2nd Law of Thermodynamics, only observed in certain spin-correlated systems fo a fraction of a second, after which normal service from the 2nd Law is resumed. Post 4 in the link points out the qualifications.

No time travel and nothing about time actually going backwards. That is just journalistic hype.

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This violates the second law of thermodynamics as well as the theory of the 'arrow of time' which states time can only flow forwards. These experiments have proven that time can work in reverse (atoms being heated up will get hotter instead of getting colder).

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The "arrow of time" idea seems to have arisen in response to the idea of 4-dimensional space-time. It refers to the fact that unlike the spatial dimensions, time seems to be assymmetrical and directional. There's a distinction between future and past that seems very different than the difference between left and right.

The difficulty for physics is that most of its mathematics is time reversal invariant. The laws of physics as currently conceived seem to work just as well whether we plug past states into the equations as our variables in order to predict future states, or whether the process is reversed, using future states as our variables in order to predict the past.

So, what in physics accounts for the assymmetry of time?

Physicists have long recognized that the second "law" of thermodynamics seems to be the only principle of mathematical physics that distinguishes between past and future. (The 'wave function collapse' speculations may conceivably provide us with another one, if that's the interpretation of q-m we accept.) So there have been many attempts to explain the assymmetry (the "arrow") of time by appealing to thermodynamics. (It seems a little circular to me.)

So, I'm personally not entirely convinced that detecting tiny violations of the second "law" of thermodynamics on the microscale tells us a whole lot about the nature and direction of time. It might just be telling us that thermodynamics is less closely tied to the direction of time than some theorists like to think.

My simplistic non-scientific perspective on the impossibility and nonsense of time travel to the past.

Time slows with increasing velocity, and at the speed of light time should become zero. To go back in time, e.g. negative time, one must exceed the speed of light, our current boundary. But energy to move mass at increasing velocity also increases at an exponential rate, and at the speed of light requires infinite energy, unless you have zero mass, or near zero, e.g. a photon. Since a person will always have positive mass, then they can forget time travel. Or in other words to go back in time requires more than infinite energy - i.e. a nonsense.

It seems easier to think of time as a 4th dimension that we can more accurately refer to as "persistence". For something to exist it must have the usual 3 dimensions, each with a non-zero positive value. It is nonsensical to consider negative length for example - doesn't have meaning. And for something to be said to exist it must also persist from one moment to the next, so "persistence" must also have a non-zero positive value. I.e. negative "persistence" has no meaning as with any dimension.

Time isn't a medium in which we can travel, that's the wrong way to think of time, instead it is simply an attribute of existence. To consider reverse time one must consider negative existence - huh?

This violates the second law of thermodynamics as well as the theory of the 'arrow of time' which states time can only flow forwards.

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Gee, makes me feel like going out and watching a street, road, highway, or railroad track flow. Or watching a tree trunk flow from the ground upward to the top. In the spirit of Flat Earth, it's a yearly delight to hear somewhere that a framework of time is still oozing along with conflicting reference to itself.

The laws of physics as currently conceived seem to work just as well whether we plug past states into the equations as our variables in order to predict future states, or whether the process is reversed, using future states as our variables in order to predict the past.

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The above is based on classical physics prior to circa 1920, which was deterministic.

Modern mainstream physics views the classical world of our senses as being based on a quantum level of reality which obeys probabilistic laws.

Radioactive decay is the most well known process governed by probabilistic rather than deterministic laws.

It is not the only process which obeys probabilistic laws, ​

From Cris Post 5

It seems easier to think of time as a 4th dimension that we can more accurately refer to as "persistence".

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Treating time as a 4th dimension results in a model of reality which is static.

The motion of a particle is viewed as a static world line in a 4 dimensional space. ​

The above is a useful model because it allows the use of a powerful field of mathematics called Differential Geometry to develop useful insights.

[...] I had a best friend die abruptly in 2013, would it be possible to go back in time to see him again?

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It never ceases to be both fascinating and disturbing how little importance is placed on the dead just still existing, period... As if from a selfish perspective it doesn't mean anything at all if one cannot visit them by time-travel. We ourselves would be deceased from the standpoint of distant enough future descendants, despite subjectively experiencing the opposite. And it's not necessarily encouraging that a Greene, Penrose, Davies, Einstein, and so-forth at least had a light-bulb illuminate in their heads with regard to the necrological implications. If the roaring whoosh over the majority of the rest of the population's heads still continued to be unabated and deafeningly unsettling.

Brian Greene (2003, NYT): And in moments of loss I've taken comfort from the knowledge that all events exist eternally in the expanse of space and time...

Roger Penrose (old documentary): I think there is a positive side to this picture of space and time being laid out there as 4 dimensions, because it tells you that all times are there once and it can affect the way one thinks about people who have died. I mean, I remember thinking in this kind of way when my mother died. In some sense she was still there because her existence is still out there in space/time although in our time she is not alive. A colleague of mine had a son who died in tragic circumstances and I presented this idea to him and it helped his understanding also. This was before I heard that Einstein had a colleague died and he wrote to the man's wife that Bessa was still out there, and that somehow this was reassuring. I certainly think this way often, that space/time is laid out and that things in the past and things in the future are out there still.

Paul Davies (2002, SciAm): Perhaps we would no longer fret about the future or grieve for the past. Worries about death might become as irrelevant as worries about birth. Expectation and nostalgia might cease to be part of human vocabulary. Above all, the sense of urgency that attaches to so much of human activity might evaporate. No longer would we be slaves to Henry Wadsworth Longfellow’s entreaty to “act, act in the living present,” for the past, present and future would literally be things of the past.

I saw Stephen Hawking on a cable show a couple of years ago and he gave one example of how to construct a time machine by building a railway line around the equator and running a train around the world 7 times per second.

I saw Stephen Hawking on a cable show a couple of years ago and he gave one example of how to construct a time machine by building a railway line around the equator and running a train around the world 7 times per second.

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Either he stole the idea from a Supermam movie
Or the movie stole his idea

I saw Stephen Hawking on a cable show a couple of years ago and he gave one example of how to construct a time machine by building a railway line around the equator and running a train around the world 7 times per second.

LOL! That wouldn't work!!! Time exists for eternity. The ONLY way to time-travel is to create something that ALSO exists for eternity (a theory, an equation), although there are infinite ways to do it. ☺

Having wrote that, if it will, "never" work, then that will remain true forever. So it will work. But if it does work, then what makes it work is voided, so it will not work. It's a paradox. The important thing is that one, "does it."

LOL! That wouldn't work!!! Time exists for eternity. The ONLY way to time-travel is to create something that ALSO exists for eternity (a theory, an equation), although there are infinite ways to do it. ☺